The proliferation of online multimedia content has the potential to make web content more accessible to all people in convenient and easy to absorb formats, but there is also the potential to render content even less accessible if appropriate steps are not taken.
- Provide a transcript for audio content
- Provide captions on video content
- Provide an audio equivalent or full text alternative for video content
- Ensure media player accessibility
- Ensure keyboard accessibility and avoid keyboard traps
- Give the user control to start, pause and stop the video or audio content
The web has seen a proliferation of video and audio content in recent years, as bandwidth has increased, and browsers and media players have improved their ability to deliver such content smoothly.
Multimedia once referred to CD-ROMs and highly interactive applications that offered choices to users to consume a variety of content across different types of media, from video and sound through to moving images, text and other interactive elements. More recently, multimedia usually refers to playing audio and/or video content within a browser and that is where this topic will focus.
This has the potential to make web content more accessible to all people in convenient and easy to absorb formats, but there is also the potential to render content even less accessible if appropriate steps are not taken.
WCAG 2.0 refers to multimedia content as time-based media because both audio content and video content depend on the passing of time to deliver the full content. It includes both pre-recorded and live-streamed content, allowing for slight differences in the requirements for the live video/audio content.
Guideline 1.2 Time-based media states:
Provide alternatives for time-based media.
This has ramifications for the provision of all online video and audio content, including:
- audio and/or video with interaction
There are nine success criteria involved — three that establish Level A conformance, two that take conformance to Level AA and another four to reach Level AAA conformance.
WCAG 2.0 notes that where time-based media presents a version of content that is also provided in text form, the time-based media does not need to be made accessible. This is because the “main” text version provides the accessible alternative to the video already. For example, if a webpage contains a complete text transcript of a speech, and a video of the speech being made is also provided, then the video does not need to be made accessible by adding captions.
Note: There is no restriction whether a single version of multimedia is enhanced to be made accessible in whatever ways required (for example by the inclusion of open or closed captions), or two versions are made available: one standard (without captions) and one accessible (with captions). In some circumstances, the former approach may be more appropriate, as it means maintaining only one resource.
You may also come across the term synchronised media. This refers to content where audio and video is synchronised to present meaningful content, for example a video slideshow with an audio track. This not only needs to be made accessible, but in such a way that the synchronisation is maintained.
It is permissible to pause an element of the presentation in order to include accessible details, but the synchronisation must remain intact. For example, if the visual element presented requires audio descriptions, the previously existing audio may need to be paused or extended in order to fit the description at an appropriate place that does not change the existing synchronisation.
At all points, the aim is to ensure that multimedia content is accessible to people with disabilities. WCAG 2.0 is designed to offer pragmatic, testable solutions to help verify this goal is achieved.